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Video transcript

Walter cannon was an American doctor in the early 1900 who spent a lot of his career expanding our understanding of homeostasis which is the tendency of our body to respond to the environment in a way that keeps the internal workings of our body stable so the body's ability to maintain the right temperature the body's ability to maintain the right pH etc so as a part of his study of homeostasis dr. cannon was really interested in the homeostatic response of animals to threats or dangers so threats or dangers and and threats or dangers are what we've been referring to as stressors so so basically dr. cannon was interested in our homeostatic response to stressors and he coined the response that he saw the fight-or-flight response because he basically saw that we were either going to prepare to fight against these threats or dangers or we were going to prepare to run away from these threats or dangers so the fight-or-flight response that cannon was so interested in it revolves around the inner workings of the nervous system and the endocrine system so on the nervous system side of things we have the sympathetic nervous system so we have our brain and our spinal cord that make up the central part of our nervous system and the nerves branch off of this central core and we have the part of our nervous system that we don't always think about or aren't thinking about to control as the autonomic nervous system and a branch of that autonomic nervous system that's going on behind the scenes is the sympathetic nervous system and this is the aspect of our nervous system that's going to transition our body into the get out of danger mode and so with that we'll see increased heart rate in order to pump blood with oxygen and nutrients all around our body so we have an increased heart rate that heart's just going to beat a lot faster and we're also going to see increased respirations so we have an increased respiratory rate that gives us the ability to get more oxygen into our blood and in all the way to our tissues and it gives us the ability to expel more carbon dioxide as a as a waste product from our muscle work and then we're also going to see increased peripheral vasoconstriction so the the blood vessels in our peripheral parts of our body like our arms and our legs are going to clamp down and they're going to tighten in order to push more blood to our core area because our arms and legs are important but we can live without them it would be a lot harder to live without our brain or our vital organs so we need a lot of our blood force into those really crucial areas so we're going to see peripheral vasoconstriction happening in this fight-or-flight response and then lastly we're going to turn off less important things like digestion and immune function and ovulation because these things are great if we're just hanging out but they're definitely less crucial in life-or-death situations so teaming up with the sympathetic nervous system we have the endocrine system and so the endocrine system is going to supply some of the hormones which remember are those chemical messages in order to rally the troops around the body and the two biggest hormone players actually come out of the same organ which sit on top of our kidneys the same organs and those are your adrenal glands and so the inside of our adrenal glands this hashed part is called the medulla and from the medula we get our catecholamine hormones and our catecholamine hormone excuse me include epinephrine and norepinephrine so sometimes those are more often called adrenaline and noradrenaline but these are the hormones that are major communicators for increasing the heart rate and blood pressure and otherwise communicating that sympathy or that sympathetic response that we just talked about so those are really supporting the sympathetic nervous system these these hormones coming out of the adrenal medulla and then on the outside this bolder part our adrenal glands that's called the cortex and out of the cortex can some other major stress hormones and the biggest one is a glucocorticoid called cortisol and it helps me remember that that cortisol comes from the cortex if I'm thinking about that Court kind of root word a root part of the word but cortisol is a steroid hormone which contributes to the stress response by redistributing glucose energy in the body and and suppressing the immune system and so just to review real quick we have this fight-or-flight response to stressors so we're preparing to either fight or to run away and that's being communicated by our sympathetic nervous system which is being assisted by the the hormones of our endocrine system and so we have this fight-or-flight response that dr. cannon and coined the the terminology but we also have another response called tend and befriend we're calling this affiliative response to tinned or befriend response because it turns out that sometimes a better response to stress is to huddle together into form support systems and an important biological component to this response is the hormone oxytocin and oxytocin is associated with things like pair bonding in and so it can moderate this stress response and it's really interesting if you know much about oxytocin it's majorly integrated with the hormone estrogen and so estrogen is a major sex hormone in women and so what follows is kind of a naturally greater disposition to this tend and befriend response in women much much more so than in men and so we had these two major kind of categories of response to stressors we had this fight-or-flight response and this tendon befriend response and in the later part of the 20th century a guy named hans selye continued the stress research of dr. canon and he was able to classify distinct stages to the adaptive fighter flight in tendon responding before an responses and he called this generalization the general adaptation syndrome so I'm going to I'm going to shorten that to GA s for general adaptation syndrome and you saw this general adaptation syndrome as having three phases and in the first phase he called it the alarm phase and then this alarm phase that stress reaction kicks in so your heart starts racing and and your resources are mobilized and you're ready to fight or to run for your life and that's the alarm phase and the second phase which he called the resistance phase and we're actually fighting or fleeing or or huddling together our temperature is elevated and our blood pressure and rate of breathing remain high and we're also bathing our body and the stress hormones like like cortisol and so our body has reserves to react to those acute stressors in this resistance phase but those reserves only go so far and that brings us to the third phase of the GA s and that's exhaustion so if the resistance stage isn't followed by recovery the body's stress resources get depleted it leads to exhaustion and our tissue and muscles become damaged in our dampen immunity can make us really susceptible to illness and an all-around overexposure to stress can have some really damaging effects because like many animals our bodies pretty well equipped to handle short-term stress but the problem is that when we apply those life-saving stress reactions to our daily commutes into our nine-to-five jobs and to other psychosocial kind of trivialities of life we end up spending way too much time experiencing the negative consequences of stress this exhaustion consequence and it has some pretty nasty consequences so next up we're going to explore what happens to our bodies behaviors and emotions when we're exposed to chronic stress